Micro-Electrical-Mechanical-Systems (MEMS) such as sensors can be widely used in applications such as automotive, household appliance, building ventilation, and in general industrial applications to sense a physical condition such as pressure, temperature, or acceleration, and to provide an electrical signal representative of the sensed physical condition.
Most sensors are sensitive to stress or strain of their physical structure in addition to being sensitive to the measurand of interest. Such stresses can be internally generated by virtue of the sensor structure itself, or can be externally generated by the sensor's enclosure, or packaging. Package stresses, such as thermal stress, can affect the output of a MEMS sensor. One example of package-sensor interaction stresses are stresses caused by the mismatch in the thermal expansion coefficient of components of the package and components of the sensor. Different methods for providing thermal stress relief from packages have been previously disclosed. Some of the conventional methods use flexible support beams to suspend the sensor element. All other conventional methods apply package bonding modification, e.g. by using flexible support diaphragm, flexible support chuck, or putting stress buffer material between the MEMS device and the package.
The conventional methods are not suitable for some MEMS pressure sensor packages. For example, the use of flexible support beams requires extra stress relief support structure, which is not hermetic and cannot withstand high applied pressure. Other conventional methods require extra parts or result in a high cost due to complex manufacturing requirements.
There is a need for stress relief structures and methods that can be applied to MEMS sensors requiring a hermetic seal and that can be simply manufactured.